Speaking only for myself, the Refresh Rate app allows for the ever-increasing amount of true 24.0 Hz content on Netflix to play correctly without being forced out at 23.967 Hz which induces an annoying frame drop every 41 secs. My primary streamer, the Apple TV4K, does not Match Frame Rate when encountering 24.0 Hz content, it forces it out at 23.967 Hz. I purchased the Shield because it would handle Netflix 24.0 Hz content properly. Crazy expensive for being primarily a Netflix streamer but given the scarcity of the Shield I'm pretty sure I'll recover my cost if Apple ever acknowledges that 24.0 Hz exists.
Not a complete list, more just a fraction, but the below link contains many Netflix Originals along with non-originals that are native 24.0 Hz.
True 24.0 Hz streaming titles
I know about Apple's blind spot with 24p - I also own the ATV4K. So since the Shield handles 24p properly, why/how do you use the Refresh Rate app? Or is there a version for the ATV4K and that's what you're using...?